P24F2: EGR Temperature/Charge Air Cooler Temperature Correlation

What it means

After a long key-off soak both the EGR temperature sensor and the charge-air cooler outlet temperature sensor must read approximately the same ambient temperature. The ECM compares them and detects an implausible delta. One of the sensors drifts, is wired wrong, or is exposed to a heat source the model does not know about.

At a glance

• Usually lights the check-engine light
• Affects emissions; the car can fail an emissions test

How it works

The exhaust gas recirculation (EGR) temperature sensor and the charge-air cooler outlet temperature sensor measure temperatures in separate parts of the engine air and exhaust systems. After a long key-off soak, the control module expects both readings to be close because both should reflect ambient temperature. P24F2 sets when the difference between those readings is implausible for the conditions.

Common causes

Most likely first.

1. One sensor drifting outside tolerance
2. Residual heat in the charge-air cooler after a hot soak

Symptoms

• Check engine light may illuminate

How to diagnose it

1. Review freeze-frame data and note how long the engine had been off, since residual heat can distort a temperature comparison.
2. After the vehicle has sat long enough to reach ambient temperature, compare the EGR and charge-air cooler outlet temperature readings on a scan tool.
3. Inspect both named sensor connectors and wiring for damage, corrosion, crossed repairs, or routing near an unaccounted heat source.
4. Compare each sensor reading with ambient temperature and with the other sensor before starting the engine to identify which reading is implausible.
5. Test the EGR temperature sensor and charge-air cooler outlet temperature sensor circuits and sensor response using the manufacturer's specification.
6. If both sensor circuits and readings are credible, check whether heat soak or a recent repair has changed the temperature conditions the plausibility model sees.

Common fixes

• Repair damaged wiring or poor connections at the EGR or charge-air cooler outlet temperature sensor.
• Correct sensor wiring or routing if a repair crossed circuits or placed a sensor lead near an unintended heat source.
• Replace the EGR temperature sensor if its cold reading or response is outside the manufacturer's specification.
• Replace the charge-air cooler outlet temperature sensor if its reading or response is outside specification.

Can I keep driving?

This code alone usually does not make the vehicle unsafe to drive, but it can impair emissions monitoring. If the engine runs normally, limit unnecessary driving and address it before an emissions inspection or if other warnings appear.